This invention relates to the inspection and repair of fossil fuel boilers and other high temperature equipment. The invention is also directed to a special heat resistant suit which permits workers to enter and perform maintenance work in boilers and other high temperature areas.
In the operation of electrical generating plants and other plants which utilize boilers (either fossil fuel or nuclear) enormous expense is incurred when the boiler develops a malfunction and must be shut down. Electric utilities usually must purchase power from other utilities at significant cost. Normally, when there is a defective boiler tube or other malfunction in the boiler, it is necessary to shut the boiler down and cool it with a fan for a full 24 hours or more in order to drop the temperature low enough to enable workmen to enter the boiler to inspect the damage and carry out the necessary repair work. The cost of having a large boiler inactive for a full day can exceed several hundred thousand dollars.
In addition to repair work, it is necessary to inspect the boilers periodically in order to detect any developing problems at an early date so that preventive maintenance can be performed to prevent severe malfunctions that could put the boiler out of operation for an extended period of time. For both inspection and repair work, the boiler is usually cooled from its normal operating temperature of approximately 2300.degree. F. to about 150.degree. F. which is the maximum temperature at which workers can operate effectively with conventional high temperature clothing and gear. When the boiler is cooled down much below 300.degree. F., the steel can crack due to the quenching effect. Also, it is undesirable to cool the boiler any more than is necessary because of the expense involved in heating it back up to its operating temperature after the repair work has been completed. Therefore, it is apparent that considerable cost savings would be possible if inspection and repair work could be performed at higher temperatures than has been possible in the past.
The present invention makes such cost savings possible by providing a method that permits maintenance and repair work on boilers and other high temperature equipment to be carried out at temperatures of 700.degree. F. or more.
In accordance with the invention, a special high temperature suit is provided which permits a worker wearing the suit to enter a boiler or the like at 700.degree. F.-1000.degree. F. and effectively perform welding and other work for several hours or more. Once the boiler has been cooled to about 1100.degree. F., workers wearing the special suit can begin setting up scaffolding in the boiler. Repair work within the boiler can begin at about 700.degree. -800.degree. F. rather than requiring a delay until the temperature has dropped to 150.degree. F. as has been necessary in the past. As a result, the downtime of the boiler can be cut nearly in half in most cases, and savings of hundreds of thousands of dollars can be achieved each time there is a malfunction that requires entry into the boiler for corrective action. Similar savings can be made in the inspection and repair of high temperature equipment in refineries, chemical plants and other industrial facilities (including precipitates and scrubbers). It is also possible to perform some inspection procedures through ductwork while the boiler remains in service, provided that the ductwork temperature does not significantly exceed 1000.degree. F.
The method of effecting repair of boilers and other high temperature equipment is made possible by a special heat resistant suit which is constructed in a unique manner and provided with a cooling system that enables it to be worn in high temperature environments for extended time periods. Refrigerated air is delivered from an external refrigeration unit through a special hose having a quick "break away" connection with the leg of the suit. The hose is insulated and also supplies air from an external compressor which facilitates breathing in the high temperature environment. In an emergency situation, the hose can be disconnected simply by a "quick coupler", and an emergency air pack carried in the suit then automatically takes over to provide 5 minutes of air which is sufficent to permit escape from the boiler.
Another safety feature of the suit is provided by a harness mounted safety reel having a safety cable with a hook on the end. If an emergency arises requiring fast escape, the safety hook can be applied to the scaffolding to permit the worker to drop in a controlled descent from the scaffolding. The reel is equipped with a hand operated friction brake which can be applied to control the speed of the fall.
Additional features of the suit include a dual welding lens arrangement on the face of the hood, a two-way radio and voice activated microphone built into the face mask, and drawstrings for maintaining the various parts of the suit tightly against one another in overlapping fashion.